The natural history and response to photocoagulation treatment will be investigated. The objective of this study is to determine if the argon laser is useful in the management of branch vein occlusion and its complications as follows: 1. Major Branch Vein Occlusion: a) Improve or maintain visual acuity; b) Improve or prevent macular edema; c) Prevent the development of neovascularization. 2. Macular Branch Vein Occlusion: a) Improve or maintain visual acuity; b) Improve or prevent macular edema. 3. Major Branch Vein Occlusion with Neovascularization: a) Improve or maintain visual acuity; b) Control or destruction of neovascularization; c) Prevention of vitreous hemorrhage and/or retinal detachment.